Polyester resins have found widespread use in varied applications. Polyester resins, such as polyethylene terephthalate and polyethylene naphthalate, are used in films, including photographic film and magnetic tape, in fibers, and in food containers such as bottles and beverage containers. Various methods have been disclosed for the depolymerization of such resins into their component monomers, such as ethylene glycol, terephthalic acid, naphthalic acid, or derivatives thereof, so that they could be reused.
U.S. Pat. No. 5,051,528 describes a process of recovering ethylene glycol and dimethyl terephthalate from polyethylene terephthalate scrap resins by dissolving the polyester resin in oligomers of the same monomers as present in the polyester, passing superheated methanol through the solution and recovering ethylene glycol and dimethyl terephthalate.
Commonly assigned, copending U.S. patent application Ser. No. 07/981,688 describes an improvement in the process of the '528 patent in which the scrap resin is combined with reactor melt in a dissolver, before the dissolver melt is transferred to a reactor for contact with super-heated methanol. In one embodiment, the polyester is combined in the dissolver with, in addition to reactor melt, other components exiting the reactor.
Other art describing recovery of monomer from polyester resins is noted in the above patent and application.